Method for dividing a material into fibers



Nov. 1, 1966 A. WALZ ET AL METHOD FOR DIVIDING A MATERIAL INTO FIBERS Filed Aug. 28, 1963 4 Sheets-Sheet l Nov. 1, 1966 ,w 1 z ET AL METHOD FOR DIVIDING A MATERIAL INTO FIBERS 4 Sheets-Sheet 2 Filed Aug. 28, 1963 Nov. 1, 1966 w z ETAL METHOD FOR DIVIDING A MATERIAL INTO FIBERS Filed Aug. 28, 1963 4 Sheets-Sheet 4 United States Patent 3,283,039 METHOD FGR DI'VIDING A MATERIAL INTG FIBERS Alfred Walz, Emmendingen, Baden, Manfred Mayer, ilIannheirn-Almeuhof, and Hans Hermann Fernhoiz, Kehlhach, Germany, assignors, by mesne assignments, to Alfred We-l2, Baden, Germany Fiied Aug. 23, 1963, Ser. No. 305,163 Claims priority, application Germany, Aug. 29, 1952, G 35,810 11 Claims. (Cl. 264-12) The present invention relates to a method for dividing a material into fibers, and more particularly to a method for making fibers of a continuously supplied molten material such as synthetics, minerals, and glass, by blowing a fluid such as steam, against a coherent stream of the material flowing out of a container. When the flowing material is impinged by a stream of fluid in a passage the flowing material is accelerated, drawn, out, and divided into fibers.

Apparatus serving this purpose is known, and it is one object of the present invention to improve the methods according to the prior art, and to provide a new method by which fibers of higher quality are produced in greater quantities.

Another object of the present invention is to provide a method which produces the same amount of fibers while using 50%, or less, of the impinging fluid than the prior art.

Another object of the present invention is to provide a method for producing very fine fibers.

Another object of the preesnt invention is to discharge the fluid stream in which the newly produced fibers are entrained, through a diffuser which is shaped in such a manner as to improve the deposition of the fibers.

Another object of the present invention is to provide a diflusor shaped in such a manner that the fluid stream does not peel off the diffusor wall, while the friction losses are held to a minimum.

In accordance with the present invention, the improved quality and quantity of the produced fibers is achieved by a better distribution of the velocity of the impinging fluid in the passage where the fibers are formed, and particularly in the space between inwardly directed streams of the fluid. In the present invention, the fluid stream carrying the newly formedfibers is guided in accordance with the boundary layer theory in such a manner that improved efficiency is obtained.

One method of the present invention comprises the steps of continuously supplying a material, such as glass, plastics or minerals, in molten condition into the inlet of a passage; and directing a fluid stream at an angle to the direction of the passage onto curved guide face means at the inlet of the passage at such a speed that the fluid stream adheres to the curved guide face means due to the Coanda effect.

The Coanda effect is a physical phenomenon according to which an expanding stream of a gas adheres to, and closely follows curved guide face means, particularly when moving at a velocity approaching the speed of sound.

The curved guide face means may comprise a pair of opposite curved guide faces, or an annular curved guide face. In any event, the outwardly located portions of the guide face means extend at an angle of between 15 and 90, and preferably 20, to the direction of the passage and of the stream of flowing material therein, while the inner surface portions of the guide face means extend substantially in the direction of the passage, or merge into the wall of the passage.

Since the fluid stream is diverted by the curved guide face means to flow substantially in direction of the passage, the material is divided into fibers, while being prevented Patented Nov. 1, I966 from contact with the guide face means and with the walls of the passage.

It is preferred to provide a diffusor at the outlet end of the passage, and to design and construct the diifusor in such a manner that fluid carrying the fibers regressively expands in the diifusor.

In accordance with the present invention, the arrangement is such that there is no increase of the velocity of the boundary layer on the divergent surface of the diffusor so that the shearing stress between the boundary layer and the diifusor surface approximates zero and no peeling olf of the boundary layer takes place. Friction in the boundary layer between the flowing fluid and the diffusor surface is completely eliminated or at least held to a minimum.

While the use ofthe Coanda effect and of a specific diflusor construction cooperate in a particularly advantageous manner, either of these two features of the invention has great utility even if used independently of the other.

In one embodiment of the invention, the guide surface is curved along a circle. In modified embodiments of the invention, the guide surface has a varying radius of curvature which may be continuously increased or decreased. It is also possible to provide a guide surface which has several regions, each of which has a different radius of curvature.

The guide means on which the curved guide surface is provided is made turnable to adjust the position of the guide surface. In another embodiment of the invention, a cover means forms a gap with the guide surface through which the fluid passes. By adjustment of the cover means, the portion of the guide surface where the fluid stream comes into contact with the guide surface, can be selected whereby the direction of the flow of the fluid is influenced.

High pressure steam is preferably used as impinging fluid since a molten material in contact with steam has less tendency to adhere to the walls of the apparatus than matterial in contact with hot gases whose temperature is above the temperature at which the material becomes adhesive. The use of steam permits the provision of a substantially narrower passage for the material and for the impinging streams which results in a greater velocity of the fluid stream in the passage in the region where the fibers are formed so that the quality of the fibers is substantially improved.

In accordance with prior art arrangements, the fluid stream was blown at an angle of about 10 to the direction of the movement of the flowing material so that the same was impinged by the fluid stream at a certain distance from the outlet from which the material flows. In accordance with the present invention, the fluid stream has a substantially greater angle to the flow of material, and consequently impinges the materal more closely to the outlet opening for the material. At the same time, the fluid is guided along the curved guide surface into the interior of the passage due to the Coanda effect, so that the molten material is not only impinged by the fluid directly after being discharged from the outlet opening, and consequently in hotter condition, but also drawn into, and divided at high speed in the passage. In the passage the flowing material is spaced by the fluid streams from the walls of the passage since the flowing material is guided by the fluid stream where the same has the highest velocity, and consequently the lowest pressure.

The passage may have the cross section of an elongated rectangle, or a circular cross section, or a polygonal cross section, and the curved guide surfaces are correspondingly constructed.

In accordance with the present invention, losses in the diffusor are held to a minimum while pressure re- '3 '0 covery and'velocity decrease are optimal, if the shape parameter of the velocity variation in the boundary layer has a constant value at every point .of the difiusor surface and is slightly less than the parameter of the diffusor shape at which detachment ofthe flowing fluid takes place. The optimal dimensions of the diffuser can be computed on this basis for incompressible and compressible boundary layer flows with turbulent boundary layers along planar or annular surfaces. It is only necessary to know the flow values at the inlet of the dilfusor, and the optimal diffusor dimensions can be calculated by approximation methods.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. both as to its construction and its method of operation together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing, in which:

FIG. 1 is a fragmentary schematic side view illustrating one embodiment of the present invention;

FIG. 2a is a longitudinal sectional view illustrating another embodiment of the invention;

FIG. 2b is a plan view illustrating the embodiment of FIG. 2a;

FIG. 3a and FIG. 3b are fragmentary schematic views illustrating modified shapes of the guide surfaces of the embodiments of FIGS. 1 and 2a;

FIG. 4 is a fragmentary sectional view illustrating a detail of the embodiment of FIG. 1 on an enlarged scale, the section being taken along line IVIV in FIG. 5;

FIG. 5 is a sectional view taken on line VV in FIG. 4;

FIG. 6 is a fragmentary cross sectional view illustrating a modification which may be applied in various embodiments of the invention;

FIG. 7 is a fragmentary cross sectional view illustrating a modification of the embodiment shown in FIGS. 1, 4 and 5; and

FIG. 8 is a diagram illustrating the flow conditions in a difiusor according to the present invention.

Referring now to the drawing, and more particularly to FIG. 1 which shows the general arrangement of one embodiment of the invention, a pair of blower means 1 and 2 are symmetrically arranged with respect to an outlet member 3 from which a molten material 4 is discharged downwardly in a vertical direction in a stream 4. Each blower means has a curved guide surface 5 which is partly covered by one of cover members 6. Fluid, such as steam, is supplied to the chambers 7, and flows through the gaps between cover members 6 and curved guide surfaces 5 so as to be discharged at the inwardly directed open ends 9 of gaps 8 onto face portions of guide surfaces 5 tangentially to the same.

As shown in FIG. 1, the inwardly directed streams of fluid are discharged from' the gap at an angle of substantially 90 to the direction of flow of the streams 4 and to the direction of the substantially parallel wall surfaces 11, 12 of passage 10 which is formed by supporting portions of the blower means 1 and 2. The above mentioned face portions extend at the same angle. The inwardly located end face portions of the curved guide surfaces 5 merge into surfaces 11 and 12 and are substantially vertical.

Due to the fact that the inwardly directed fluid streams move at approximately the speed of sound, the streams do not impinge in horizontal direction on the stream of material 4', but adhere to the curved guide surfaces 5 and diverted to flow finally in the vertical direction of passage 10 substantially parallel to the stream of material 4' and to the confronting surfaces 11 and 12 of passage 10. The curving streams of fluid provide the narrowing inlet with fluid cushions so that the continuous stream 4' cannot come into contact with the guide The invention itself, however,

surfaces 5 or with the surfaces 11, 12 of passage 10. At the same time, the iopposing'fiuid streams guide the flow of material 4' to the center of the passabe 10 where the division into fibers takes place due to the high speed of the fluid stream in passage 10. The surfaces 11 and 12 have been described as substantially vertical, but actually converge slightly and at the narrowest point of passage 10, the division into fibers takes place. Members 1 and 2 carry bearings 15" secured thereto by screws 17, and tubular members 16, which are provided with the guide surfaces 5 are mounted on the bearing 16 by means of shaft portions 16' which permit a turning of the tubular members 15, as will be described hereinafter in greater detail. bers 1 and 2,and consequently the transverse-spacing between surfaces 11 and 12 and guide surfaces 5 can be adjusted, and when the passage 10 is made narrower, the fluid moves therein at a higher speed, resulting in better division into fibers and in higher efiiciency. V

The blower outlets 9 are symmetrically arranged with respect to a vertical plane of symmetry passing through the outlet of outlet member 3, but an asymmetrical arrangement is also possible.

Two diffusor walls 14 are respectively secured to members 1 and 2, and form a diifusor passage at the end of passage 10. The diffusor permits expansion of the fluid stream, and is designed in accordance with the present invention to achieve particularly advantageous flow conditions, as will be described hereinafter in greater detail. The passage 10 formed by diffusor walls 14 is elongated and rectangular in a horizontal cross section, and a plurality of outlet members 3 are advantageously arranged along the cylindrical guide surfaces 5 and passage 1%. The guide surfaces 5 confront each other, and have opposite portions which are straight in axial direction of the tubular members 15 corresponding to generatrices of the respective cylinder surface.

While the guide surfaces 5 shown in FIG. 1 are circular, in the modified construction of FIG. 3a the radius of curvature varies and surfaces 5 have a greater radius of curvature at the outwardly located portions thereof, and a smaller radius of curvature of the inner portions thereof which lead into the passage 1%.. In the modification of FIG. 3b, the arrangement is reversed, and the outwardly located portions of the guide surfaces 5" have a smaller radius of curvature than the inner portions which lead into passage 10. The curvature of the guide surfaces may be selected in accordance with the prevailing conditions, such as speed of the-fluid, or the kind of fluid used. Steam is preferably applied to prevent a sticking of the molten material to the walls of the apparatus.

The apparatus shown in FIG. 1 will operate even if used without diffuser, or with a conventional diffuser which is not designed in accordance with the present invention. However, the best efficiency and optimal results are achieved if the apparatus is provided with a diffusor in accordance with the present invention.

An apparatus corresponding to FIG. 1 is illustrated in FIGS. 4 and 5 on an enlarged scale so as to more clearly show constructive details of a practical embodiment. Only one-half of the apparatus is shown, and the other half is symmetrical to the illustrated half. Each support member 15 has a circular bearing face on which the cylindrical and tubular member 16 is mounted for turning movement. Tubular member 16 is fixed to two shaft portions 16a of a shaft which has a narrower portion 16 and two journal portions 16 which are located in bearing members 16". A screw 17 passes through a bore in member 15 and into a threaded hole of bearing member 16 so that the shaft, and tubular member 16 can be secured in an adjusted turned position.

The outer surface of tubular member 16 is partly covered by a cover member 18 which forms a gap with a curved outer surface of tubular member 16. A duct 20 connects the chamber formed within tubular members 16 The distance between mem-- by the thinner shaft portion 16' with the outer surface of tubular member 16 in the region of the cover member 18.

Another duct 21 connects this chamber with a curved chamber 25 extending along the outer surface of tubular member 16 in support member 15. Chamber 25 communicates through a conduit 22 with a conduit in a connecting member 23 to which an inlet pipe for a fluid, such as steam, is welded.

Consequently a fluid supplied through conduit 22 and passing into chamber 25 will enter the interior of tubular members 16 through duct 21, and will pass through duct 20 to gap 19 to be discharged from the same in inward direction along a portion of the curved outer guide surface of tubular member 16. A packing ring 24 is provided between members 15 and 23.

When screws 17 of the two symmetrical parts of the apparatus are loosened, the tubular members 16 can be turned a certain angle while the supply of fluid is not interrupted due to the circumferential extension of chambers 25. Since cover members 18 are secured by screws 26 to tubular members 16, the outlet of gap 19 is moved inwardly to a position more closely spaced from the following material 4' which is discharged from outlet member 3. At the same time, the angle between the fluid stream and the vertical stream of material 4 is varied and is no longer 90.

An angle between 15 and 90 may be used in accordance with the present invention, and an angle of 20 is preferred.

As explained above, irrespective of the position of the outlet gap 19, and the direction of the discharged fluid stream, the fluid stream will adhere to the curved guide surface of tubular member 16, and will be guided along the same and into the passage between members 15. The fluid streams will divide the material 4' into fibers, and will carry the fibers into the diffuser 14, expanding particularly at the throat 1400f the diffuser 14. Supporting members 15 are supported at both ends by shaft portions fixed thereto, and supported in suitable supports, not shown, permitting the movement of support members 15 toward and away from each other to vary the dimensions of the passage, and which may permit also a turning movement of support 15 to vary the angle between the surfaces of the passage and between the diflusor walls.

In the embodiment illustrated in FIGS. 4 and 5, the outer guide surfaces of the tubular members 15 are circular, so that the conditions remain unchanged when the tubular members are turned with cover 18.

In the modified embodiment shown in FIG. 7, the cover member 18 is provided with slots 26 through which screws 26 pass. This arrangement permits an adjustment of the cover members 18 and a corresponding displacement of the outlet opening of gap 19 in circumferential direction of tubular member 16. Screw 26 is tightened in a selected position of cover member 18'. This construction eliminates the necessity of turning tubular member 16. When the outer guide surface of tubular member 16 is constructed to have a varying curvature described with reference to FIGS. 3:: and 3b, the adjusting means of FIG. 7 are particularly advantageous.

Another modified construction of the present invention is shown in FIG. 6. Cover members are omitted, and a tubular member 33 whose outer surface constitutes a guide surface for the fluid stream, is provided with a tangentially extending duct 34 through which the fluid is discharged from the interior of tubular member 33. As explained with reference to the other embodiments of the invention, the tangentially discharged fluid stream adheres to the curved outer surface of tubular member 33 due to the Coanda effect, and is guided into the passage to divide the stream of material 4' into fibers.

The embodiment of FIGS. 2a and 21; operates on the same principle as the above described embodiments, but instead of two confronting surfaces for guiding a stream of fluid, the apparatus is substantially tubular. A tubular body 36 has a tubular diffuser 31 with an inner annular surface 31'. The upper portion of body 313 includes a circular wall Btla forming a passage 36. An annular curved guide surface 36b is provided at the upper edge of tubular portion 30a and is curved in radial planes passing through a central vertical line of symmetry. The curvature is either circular, or in accordance with the modificat-ions shown in FlGS. 3a and 3b.

Support body 36 has another tubular partion 3110 provided with the outer thread on which a cap-shaped cover member 29 is mounted. Cover member 29 has an annular curved inner surface portion forming an annular gap 32 with the guide surface 3%. The gap 32 corresponds to gap 19 described with reference to FIGS. 4 and 5, but is circular with its center located in the vertical line of symmetry passing through the outlet of outlet member 3.

An annular chamber 28' is formed between tubular portions 39a and 3% and can be supplied with pressure fluid through an inlet 28. The pressure fluid passes through the annular gap 32, and adheres to the guide surface 30b to the Coanda effect. Consequently, an annular stream of fluid passes through gap 32, and forms a stream in passage 30' by which the material 4' is drawn and divided into fibers. The stream with the fibers entrained therein passes through the diffuser 31.

The outer circular portion of guide surface 30b along which the fluid stream is discharged is substantially constant for one cover means 29. If it is desired to change the angle of the fluid stream, another cover 29 is substituted whose central opening is bounded by an edge extending along a circle of greater or smaller diameter, so that a different portion of the curved guide surface 30b receives the fluid stream, corresponding to the different angle of the fluid stream.

The emciency of the arrangements of the present invention is further increased when the diffuser is constructed in such a manner that, without a detachment of the flow from the diffuser surface, the losses in the diffuser are held to a minimum.

This aspect of the present invention is based on the boundary layer theory according to which losses caused by the diffuser shape are reduced to a minimum, while at the same time the pressure recovery, the velocity decrease and the efficiency of the arrangement reach an optimum. This is accomplished by maintaining the shape parameter of the velocity variation of the boundary layer at every point of the diffusor contour at a constant value which is slightly below the shape parameter at which detachment of the flow takes place. Equations, or more particularly differential equations, can the set up for incompressible and compressible boundary layer flows, with a turbulent boundary layer, and with boundary layers in diffusor passages of the type described with reference to FIG. 1, and other diffuser passages described with references to FIG. 2:1. It is only necessary to know the initial conditions at the inlet of the diffusor, that is the values defining flow at the diffusor inlet.

The equations are different for incompressible turbulent boundary layers, and for compressible boundary layers, and are also different for dififusors having confronting surfaces as described with reference to FIGS. 1, 4 and 5, and four diifusors having annular surfaces as described with reference to FIG. 2a.

The boundary layer of a flowing stream is the outer portion of the flow whose velocity is smaller than 0.99 times the velocity of the core of the flow. A flow is considered incompressible below 0.3 Mach, and compressible above 0.3 Mach.

The cross section of the dilfusor at any point thereof can be calculated using the continuity equation after the velocity of the flow at the respective point has been 7 determined in accordance with one of the following equations:

' The thickness of the boundary layer being 6, the following equation is valid for an incompressible turbulent boundary layer For a diffuser according to FIGS. 1, 4 and 5, a is 0.02798, and b is 0.2105. In the above equation it indicates the speed in direction of the difiusor surface spaced at a distance 5 as shown in FIG. 8.

For a diffuser according to FIG. 2a, a is 0.02454 and b is 0.24. V

' For a diffuser according to FIGS. 1, 4 and 5, with a compressible turbulent boundary layer, the following equation is valid.

For a diffuser according to FIG. 2a with a compressible turbulent boundary layer, the following equation is valid:

In the above equation:

(ufihm secis the velocity of the flow at diffuser inlet at the beginning of the expansion. (Re5 is the Reynolds number at the diffuser inlet (x=0) calculated for the momentum loss thickness x[m] is the coordinate in flow direction, being zero at the diffuser'inlet. 6 [m] :momentum loss thickness.

Due to the fact that the flow must adhere to the wall of the diffuser, and should not peel off, the velocity drops in a layer of the boundary layer toward the diffuser surface and is zero at the diffuser surface. Due to the drop of velocity across the boundary layer, a shearing force is effective which depends on the velocity gradient. Conversely, the velocity will increase in the boundary layer in the direction from the diffuser surface toward the inner flow, and in accordance with the present invention, the diffuser cross section is increased dependent on the above equations so that the increase of the velocity at the diffuser surface is zero. This is the maximum expansion, and when the same is exceeded the fluid stream will be detached from or peel off the diffuser surface. In this event, a rearward flow takes place along the diffuser surface which causes the separation of the flowing medium from the wall of the diffuser.

FIG. 8 is a diagram illustrating the velocities it over the cross section of the diffuser llDlCt 14a. The coordin- .ate x is zero at the diffuser inlet, and is parallel to the axis of the diffuser. The coordinate y is transverse to the flow direction and is zero at the diffuser wall.

In accordance with the invention, the angle between the tangent on graph u and the y coordinates, is zero at the point y=0,

Consequently, the sheaning stress (in in)...-

the fluid to regressively expand in a direction transverse I to a flow direction.

It will be'understood that each of the elements described above or two or more together, may also find a useful application of other types of methods and apparatus for guiding a fluid into a passage differing from the types described above.

While the invention has been illustrated and described as embodied in a method and apparatus for dividing a material into fibers by a flu id stream diverted by the Coanda effect, and expanding in a diffuser with a minimum of friction losses, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore such adaptations should and are intended to be comprehended within the meaning and range of equivalence of'the following claims.

What is claimed and desired to be secured by Letters Patent is:

1. A method for dividing a material comprising con tinuously supplying the material in one direction into the inlet of a passage extending in said direction; and directing fluid at an angle to said direction onto curved guide face means at such a speed that the fluid adheres to said curved guide face means due to the Coanda effect and flows along the same; and disposing at least one face portion of said guide face means in the region of said inlet substantially in said direction whereby the fluid is diverted by said curved guide face means to flow substantially in said direction into said passage so that the material is divided by said fluid while being prevented from contact with said guide face means and with said passage.

2. A method for dividing a material comprising continuously supplying the material in one direction into the inlet of a passage extending in said direction; and directing fluid at an angle to said direction onto at least one first face portion of curved guide face means defining with said direction substantially the same angle, and at such a speed that the fluid adheres to said curved guide face means due to the Coanda effect and flows along said curved guide face means; and disposing at least one end face portion of said guide face means adjacent said inlet substantially in said direction whereby the fluid is diverted by said curved guide face means to flow substantially in said direction into said passage so that the material is divided by said fluid while being prevented from contact with said guide face means and with said passage.

3. The method set forth in claim 2 wherein said angle is between 15 and and wherein said direction is vertical.

4. A method for dividing a meltable material such as glass, plastics, and minerals into fibers, comprising the steps of continuously supplying the material in molten condition in one direction into the inlet of a passage extending in said direction; and directing a pair of fluid streams from opposite sides of said material at predetermined angles to said direction onto first face portions of a pair of curved guide faces defining with said direction substantially the same angles, and at such speed that the fluid streams respectively adhere to said curved guide faces due to the Coanda effect and flow along said curved guide faces, respectively; and disposing the end face portions of said curved guide faces adjacent said inlet substantialiy in said direction merging into the wall surfaces of said passage whereby the fluid streams are diverted by said curved guide faces to flow substantially in said directio into said passage so that the material is divided by said "id streams while being prevented from contact with said guide faces and with said wall surfaces of said passage.

A method for dividing a material comprising continuously supplying the material in one direction into the inlet of a passage extending in said direction; directing fluid at an angle to said direction onto curved guide face s at said inlet of said passage at such a speed that the fluid adheres to said curved guide face means due to the Coanda eflect and is diverted by said curved guide face means to flow substantially in said direction into said passage so that the material is divided by said fluid while being prevented from contact with said guide face means and with said passage; and regressively expanding in a direc tion transverse to said direction, said fluid carrying the divided material in a diffuser following the outlet of said passage.

6. A method for dividing a meltable material such as glass, plastics, and minerals into fibers, comprising the steps of continuously supplying the material in molten condition in one direction into the inlet of a passage extending in said direction; directing fluid at an angle to said direction onto curved guide face means at said inlet of said passage at such a speed that the fluid adheres to said curred guide face means due to the Coand'a effect and is diverted by said curved guide face means to flow substantially in said direction into said passage so that the material is divided by said fluid while being prevented from contact with said guide face means and with said passage; and regressively expanding in a direction transverse to said direction, said fluid carrying the divided fibers in a diffuser following the outlet of said passage.

7. A method as set forth in claim 6 wherein the boundary layer of said fluid stream in said difluser having a thickness flows at a velocity of less than 0.3 Mach and is incompressible and turbulent; wherein said fluid stream flows in a direction x in said diffuser; and wherein the transverse expansion of the fluid stream is computed from the velocity of the fluid stream according to the following equation:

in which (u5) [m sek is the velocity of the fluid stream at the beginning of the expansion at the diffuser inlet (x O), 5 bit] is the momentum loss thickness of the boundary layer, (Re6 is the Reynolds number at the point x=0 calculated for the momentum loss thickness 6 x[m] is the coordinate in flow direction, beginning at the diffuser inlet, and a and b are constants depending on the diffuser construction.

8. A method as set forth in claim 7 wherein said fluid stream expands between confronting diffuser surfaces having parallel straight portions; and wherein a is 0.02798 and b is 0.2l05.

9. A trod as set forth in claim 7 wherein said fluid stream ands within a surface of revolutions of said diffuse-r; and wherein a is 0.02454 and b is 0.24.

it). A method as set forth in claim 6 wherein the boundary layer of said fluid stream in said diffuser having a thickness 5 flows at a velocity of more than 0.3 Mach and is compressible and turbulent; wherein said fluid stream flows in a direction x in said diffuser between confronting diffuser surfaces having straight parallel portions; and wherein the transverse expansion of the fluid stream is computed from the velocity of the fluid stream according to the following equation:

11. A method as set forth in claim 6 wherein the boundary layer of said fluid stream in said diffuser having a thickness 5 flows at a velocity of more than 0.3 Mach and is compressible and turbulent; wherein said fluid stream flows in a direction x in said diffuser within a surface of revolution; and wherein the transverse expansion of the fluid stream is computed from the velocity of the fluid stream according to the following equation:

References Cited by the Examiner UNITED STATES PATENTS 1,659,291 2/1928 Hall 264l2 1,356,679 5/1932 Williams et a1.

2,515,738 7/1950 Slayter et al -16 3,GG9,265 11/1961 Monson et al. 26412 ROBERT F. WHITE, Primary Examiner.

ALEXANDER H. BRODMERKEL, Examiner.

I. R. HALL, Assistant Examiner. 

1. A METHOD FOR DIVIDING A MATERIAL COMPRISING CONTINUOUSLY SUPPLYING THE MATERIAL IN ONE DIRECTION INTO THE INLET OF A PASSAGE EXTENDING IN SAID DIRECTION; AND DIRECTING FLUID AT AN ANGLE TO SAID DIRECTION ONTO CURVED GUIDE FACE MEANS AT SUCH A SPEED THAT THE FLUID ADHERES TO SAID CURVED GUIDE FACE MEANS DUE TO THE COANDA EFFECT AND FLOWS ALONG THE SAME; AND DISPOSING AT LEAST ONE FACE PORTION OF SAID GUIDE FACE MEANS IN THE REGION OF SAID INLET SUBSTANTIALLY IN SAID DIRECTION WHEREBY THE FLUID IS DIVVERTED BY SAID CURVED GUIDE FACE MEANS TO FLOW SUBSTANTIALLY IN SAID DIRECTION INTO SAID PASSAGE SO THAT THE MATERIAL IS DIVIDED BY SAID FLUID WHILE BEING PREVENTED FROM CONTACT WITH SAID GUIDE FACE MEANS AND WITH SAID PASSAGE. 